数字化X线牙片和体视显微镜测量根管锥度的体外研究

An in vitro study on taper of root canal by use of digital X-ray system and stereomicroscope

目的：通过数字化X线牙片和体视显微镜测量根管锥度，获得下颌第一前磨牙根管的初始锥度，为根管器械材料的锥度设计和临床正确选择锥度器械提供参考。方法：应用数字化X线牙片机，采用平行投照技术，分别从颊舌向和近远中向对23个13～23岁下颌第一前磨牙（单根管）根管进行摄片，通过相应图像分析软件对根管冠、中、根尖各段的管径及长度进行测量；然后通过制样机对同组样本1mm等距离磨除，利用体视显微镜对断面根管管径进行摄片及测量。分析整理数据，通过相应数学公式计算各组根管锥度。结果：通过X线片得到根管近中远中向锥度分别为0．03、0．07、0．09；颊舌向分别为0．09、0．24、0．19。体视镜得到近中远中向锥度0．07、0．06、0．07；颊舌向为0．15、0．24、0．17。两种方法所得对应结果经t检验均无显著性差别，（P〉0．05）。结论：①13—23岁下颌第一前磨牙根尖1／3段的锥度近中远中向为0．07～0．09，颊舌向为0．17～0．19，对于该年龄段根管，0．07—0．09锥度器械较适合；②数字化X线牙片平行投照可准确得到该牙根管的锥度；③该组牙颊舌向根管的中1／3段锥度明显大于冠1／3段，根管预备中可导致根管冠1／3段（尤其是根管口）颊舌侧壁的过度切割。

AIM： To determine the root canal initial taper of mandibular first premolars by use of digital X - ray system and stereomicroscope, which can contributed to design the shape of preparation instruments and select the instrument＇s taper during root canal therapy. METHODS： 23 extracted single root untreated human mandibular first premolars （mean age = 18; range 13 223 years） were selected. Each tooth was radiographed by digital X- ray system. Diameters of cervical, middle, and apical third of the canals were measured with a imaging software. Then the teeth were embedded in resin. With help of sample preparation equipment, the resins were robbed off in a thickness of 1 mm perpendicular to the long axis of the tooth. For each cross section, bucco - lingual and mesio - distal diameters of the canal were measured under stereomicroscope. Finally the taper were calculated and analyzed. RESULTS： By use of digital X - ray system , the average taper of cervical, middle, and apical third of these root canals were ： 0.09,0.24, 0.19 bucco - lingually and 0. 03,0. 07 ,0. 09 mesio - distally. Under stereomicroscope the taper were 0.15 ,0. 24 ,0.17 and 0. 07,0. 06,0. 07 respectively. NO difference was observed between two measurement methods about the canal taper by t - test（ P 〉 0.05 ）. CONCLUSION ： （1） The results showed that the taper of the apical third were 0.17 - 0.19 for the bucco - lingual ： and 0.07 - 0.09 for mesio - dista. Obviously the taper of instruments between 0.07 - 0.09 is suitable for preparing the mandibular first premolar at the age of 13 - 23. （2） By digital X - ray system with parallel project, we can obtain the canal＇s taper precisely . （3）The largest taper instruments may increase the reduction of root structure （ especially at lingual and buccal canal wall）, because the original bucco - lingual diameter of these root canal orifice is smaller than the diameter of middle area of cervical third .